Category

Published on

29 Mar 2016

Abstract

The Nano Heatflow tool allows users to explore the time evolution of kinetic and potential energy among the vibrational modes of a carbon nanotube over the course of a molecular dynamics (MD) simulation. It is possible to observe the cascade of vibrational energy through the modes of the system as a non-equilibrium population of phonons is dissipated towards thermal equilibrium, and thus gives insight into the intrinsic sources of damping and dissipation within nanoscale objects. A future version of this tool will allow systems consisting of more than one nanotube, in order to illustrate the mechanisms of heat transfer between nanoscale objects.

Nano Heatflow demonstrates the insight that can be gained with this form of post simulation data analysis. So, while in principle the mode tracking algorithms can be used to analyze the trajectories from any MD simulation, on the NanoHub it is currently restricted to studying dissipation in relatively short lengths of isolated single-walled carbon naotubes, where the MD simulation of the tube are set up and run in the tool as a seamless part of the mode tracking demonstration. The user is able to select the chiral index (n,m), and length of the tube they wish to simulate (with some restrictions on the overall system size). The user then defines the configuration for a micro-canonical classical MD simulation (number of timesteps, step size, etc). The initial conditions of the nanotube are currently restricted to the exitation of single vibrational modes, some of which are low-frequency and more easily visualized. A future version of the tool should allow the nanotube atoms to be given more complex initial velocities.

The results of the MD simulation and analysis are presented in several ways. Users can view a contour plot showing total energy vs. time/mode frequency (interpolated if necessary), as well as download this data for their own analysis. Energy vs. frequency plots are also provided for each MD frame that was analyzed. The motion of the atoms in the nanotube can also be visualized using the Nanovis player. Finally, the raw output data from LAMMPS is provided for download.

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Molecular Dynamics calculations are performed using LAMMPS
Nanotube coordinates generated by TubeGen Online